JPH0357585A - Method and device for piercing printed circuit board - Google Patents

Abstract

PURPOSE:To obtain a straight hole shape by moving a focal position of an energy beam of a laser, etc., as piercing advances. CONSTITUTION:A laser oscillating machine 1 uses a pulse oscillation generated by a carbonic acid gas laser, etc. An oscillated beam is curved by a total reflection mirror 2, passes through a condenser lens 4 and executes piercing aligning a focus to a work 6 (glass epoxy material for a printed circuit). The condenser lens 4 is attached to a Z axis stage 3 with a pulse motor, and also, this stage is controlled by a focusing and laser oscillation control unit 5. From this control unit 5, signals for starting the laser oscillation and starting the working of a pulse motor stage are generated. In this state, the condenser lens 4 descends by interlocking with the laser oscillation, by which piercing can be executed by aligning a focus by the condenser lens 4 with a working position. In such a way, a straight hole shape is obtained, and a through-hole shape having high reliability can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for drilling holes in a printed circuit board using an energy beam such as a laser.

[Conventional technology 1] Conventionally, in the formation of through-holes in printed circuit boards, a mechanical processing method using a drill has been used as the drilling process.In particular, as the diameter of the through-holes to be processed becomes smaller, an expensive method with high physical strength is used. Hole drilling was performed using a carbide drill.

FIG. 3 is a diagram showing conventional hole drilling using a drill.

FIG. 3(a) shows a cross section of a hole drilled in a double-sided epoxy board 6 with a drill 9. According to this method, as shown in the figure, random irregularities are formed on the hole wall surface or the upper and lower surfaces are formed by shooting with the drill. As shown in FIG. 3(b), if a conductor is formed in such a through hole, the conductor cannot be formed uniformly, resulting in poor conduction.

[Problem to be Solved by the Invention 1] However, in view of the above-mentioned problems with mechanical drilling using a drill, micromachining using an energy beam such as a laser has been developed in recent years.

In this drilling process using an energy beam, as the beam is narrowed down, the energy density increases and the processing area becomes smaller, and the finer the hole drilling becomes, the more advantageous it becomes in terms of accuracy and cost.

However, in the case of drilling holes in printed wiring boards, depending on where the focal point with the highest energy density and the smallest spot diameter is set relative to the thickness of the board, the diameter of the hole on the laser incidence side, the exit side, or inside the hole is determined. This results in a so-called tapered shape, which causes problems such as the front and back hole diameters not being consistent due to deflection of the substrate, and sharp corners forming where stress is concentrated and resulting in a lack of reliability.

The present invention has been developed to solve the above problems.

[Means to solve the problem]

The above problem is solved by the present invention, which is characterized in that when drilling a printed wiring board using an energy beam such as a laser, the focal position of the beam is moved as the drilling progresses. When drilling a hole in a board and using an energy beam such as a laser to drill a hole in a printed wiring board, a condensing optical system is moved in the optical axis direction as a means of moving the focal point of the beam as the hole progresses. This problem can be solved by a printed wiring board drilling device characterized by having a mechanism for moving the printed wiring board.

[Effect]

According to the present invention, the position of the focal point where the energy density is the highest and the beam spot diameter is the smallest is shifted to the advancement method in accordance with the progress of the removal of the material for drilling, thereby reducing the amount of material that appears due to the removal. By moving the condensing optical system in the optical axis direction so that the focal point is always on the new surface and drilling holes in the substrate, we can create
A straight hole shape can be obtained. By making these holes conductive, it is possible to obtain a printed wiring board having highly reliable through holes.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1(a) is a diagram showing the basic configuration of a hole punching means for a printed circuit board according to an embodiment of the present invention.

In the figure, numeral 1 indicates a laser oscillator, and in this embodiment, pulse oscillation by a carbon dioxide laser (n=10.6 μm) or an excimer laser (K. rF. original=248 nm) is used. The beam emitted from this laser oscillator 1 is bent by a total reflection mirror 2, passes through a condensing lens 4, and passes through a workpiece 6 (glass-epoxy material for printed cotton boards, TLC-W-551; manufactured by Toshiba Chemicals). Drill a hole in the workpiece by focusing on .

In addition, in the figure, 7 is a stage for holding the substrate.

In this embodiment, the condenser lens 4 is attached to a Z-axis stage 3 with a pulse moder, and this stage further includes a focusing and laser oscillation control unit 5.
controlled by

Here, the control unit 5 issues signals to start laser oscillation and start lowering the pulse motor stage, and the condensing lens 4 moves down in conjunction with the laser oscillation.
Holes can be drilled by aligning the focal point of the condenser lens 4 with the processing position.

FIG. 1(c) schematically shows the situation at that time. Initially, the condenser lens 4 is located at the 4-1 position, and its focal point is located on the surface of the substrate 6. As the processing progresses, the control unit 5 controls the condenser lens 4 to 4-2.
4-3 from the position (the focal point is near the center of the substrate 6 in the thickness direction)
position (the focal point is located on the back surface of the substrate 6). As a result, the center of the beam spot is always located on the processed surface, and as a result, a uniform and straight through hole 8 can be obtained.

In the above embodiments, a laser beam such as a carbon dioxide laser or an excimer laser is used as an energy source for processing, but other energy beams such as an electron beam or an ion beam may also be used. Furthermore, in the above embodiment, the focal position is moved by moving the optical system (mainly the focusing lens) in the optical axis direction, but it is also possible to change the focal length by adjusting the thickness of the lens. It is. Furthermore, although the processing according to this embodiment is limited to drilling, it can also be applied to other processing such as cutting and welding.

Comparative Example: Fig. 2 shows processing in a case where the lens is fixed and the focal position is fixed as usual, as a comparative example of the above embodiment, and it shows that a tapered hole 8 is likely to be formed depending on this processing. .

[Effects of the Invention] As explained above, by moving the focal point where the energy density is the highest and the beam spot is the smallest as the drilling surface progresses in the depth direction,
A straight hole shape and a highly reliable through hole shape can be obtained.

[Brief explanation of drawings]

FIG. 1(a) is a diagram showing the basic configuration of a means for punching holes in a printed circuit board according to an embodiment of the present invention, and FIG. 1(b) is a block diagram of control regarding the device shown in FIG. 1(a). FIG. 1(c) is a diagram schematically showing a state in which a hole is drilled by the processing method shown in FIG. 1(a), and FIG. 2 shows a comparative example of the embodiment according to the present invention. FIG. 3 is a schematic cross-sectional view showing a hole drilling process using a conventional drill. 1... Laser oscillator 2... Total reflection mirror 3... Pulse motor stage 4... Condensing lens 5... Control system unit 6... Substrate 7... Processing table 8...・Processed hole 9...drill

Claims (3)

[Claims] (1) A method for making holes in a printed wiring board, characterized in that when making holes in a printed wiring board using an energy beam such as a laser, the focal position of the beam is moved as the drilling progresses. (2) In the above-mentioned processing method, when drilling a hole, the focal position of the beam is moved in accordance with the drilling progress method as the hole is drilled, thereby obtaining a straight hole shape without tapering. The method of making holes in a printed wiring board according to claim 1, characterized in that: (3) When drilling a hole in a printed wiring board using an energy beam such as a laser, a mechanism for moving the condensing optical system in the optical axis direction is used as a means to move the focal point of the beam as the hole progresses. A device for drilling holes in a printed wiring board, characterized by comprising: